The present invention relates to a novel process for preparing (S)-1- 2(S)-(1,3-dihydro-1,3-dioxo-isoindo-2-yl)-1-oxo-3-phenylpropyl!-1,2 ,3,4-tetrahydro-2-pyridine-carboxylic acid methyl ester which is a useful intermediate in the preparation of 4S- 4.alpha., 7.alpha.(R*), 12b.beta.!!-7- (1-oxo-2(S)-thio-3-phenylpropyl)amino!-1,2,3,4,6,7,8,12b-oc tahydro-6-oxo-pyrido 2,1-a! 2!benzazepine-4-carboxylic acid and 4S- 4.alpha., 7.alpha.(R*), 12b.beta.!!-7- (1-oxo-2(S)-acetylthio-3-phenylpropyl)amino!-1,2,3,4,6,7,8, 12b-octahydro-6-oxo-pyrido 2,1-a! 2!benzazepine-4-carboxylic acid and pharmaceutically acceptable salts thereof which are useful as inhibitors of enkephalinase and angiotensin converting enzyme European Patent Application No. 0 481 522 A1, published 22 Apr. 1992! and to novel intermediates thereof.
The process and intermediates of the present invention provide a novel enantiospecific method for preparing (S)-1- 2(S)-(1,3-dihydro-1,3-dioxo-isoindo-2-yl)-1-oxo-3-phenylpropyl!-1,2 ,3,4-tetrahydro-2-pyridine-carboxylic acid methyl ester.